arXiv subjects

Antonis Kalogirou

Publications and source records attributed to Antonis Kalogirou.

4 recordsLinked to original sources

arXiv2026

The thermal backreaction of a scalar field in de Sitter spacetime. II. Spectrum enhancement and holography

We study a spacetime obtained from the semi-classical backreaction computed via the Thermofield dynamics approach in the Poincare patch of de Sitter spacetime. The resulting bulk equation takes the Whittaker form and we examine two distinct applications. At leading order, the co-moving curvature perturbations are shown to match a constant-roll model in the frozen attractor regime, corresponding to a UV enhancement of the spectrum with $n_S \sim 2$. This blue tilt arises only for modes exiting the horizon during a transient late-time phase of inflation and therefore does not affect perturbations in the CMB scale. In the holographic context, we compute the CFT two-point function at the future boundary, and away from it we construct the flow-equation of the dual QFT that matches the beta-function of the Sp(N ) model in three dimensions.

hep-th↗

arXiv2025

The thermal backreaction of a scalar field in de Sitter spacetime

We argue that a scalar field in de Sitter spacetime should feel explicit thermal effects associated with its curvature. Starting from the Bunch-Davies vacuum and a scalar field with small mass compared to the de Sitter curvature, we use the thermo-field dynamics formalism in order to expose these thermal effects. We compute the thermal Wightman function connecting two spacetime points and from it, via the point-splitting regularization technique, the renormalized thermal energy-momentum tensor. We then examine how these corrections affect the de Sitter geometry by solving for the semi-classical backreaction and find that their sign depends on the initial conditions. In order to place our results in context, we compare them to the corresponding 2-loop quantum gravity correction to the cosmological constant derived in [1].

hep-th↗

arXiv2023

Thermal effects in Ising Cosmology

We consider a real scalar field in de Sitter background and compute its thermal propagators. We propose that in a dS/CFT context, non-trivial thermal effects as seen by an 'out' observer can be encoded in the anomalous dimensions of the $d = 3$ Ising model. One of these anomalous dimensions, the critical exponent $η$, fixes completely a number of cosmological observables, which we compute

hep-th↗

arXiv2023

Ising Cosmology

Using arguments from holography we propose that the deviation of the cosmological spectral index $n_S$ of scalar fluctuations from unity may be controlled almost entirely by the critical exponent $η$ of the $d = 3$ Ising model

hep-th↗